1. Field
Various embodiments presented and described herein relate to a technique and device of appropriately detecting a specific position of an acquired image.
2. Description of the Related Art
As society becomes more information-oriented, the leakage of confidential information is becoming a serious problem. As a result, technologies are being developed to prevent the leakage of information of not only digital data but also printed materials. For example, there is a typical technique for preventing the leakage of information from printed materials by visually encrypting information so as to hide the information from third parties before printing. With this technique, an encrypted image in the printed material is read by a scanner or camera and the original information can be seen by implementing a recovery process that uses a decryption key (for example, a password) for the image.
Japanese Laid-open Patent Publication No. 2008-301044 describes a technique of placing markers used for detecting a position of an encrypted image region at the four corners of a rectangular encrypted image region on printed material to make identification of an encrypted image region easier. Japanese Laid-open Patent Publication No. 2009-232233 describes a technique that allows restoring a partial image of an encrypted image region by saving a region of the partial image located by the markers ahead of time and then, when decrypting the encrypted image region, combining the saved partial image with the decrypted image region based on the marker placement.
For example, a more precise encrypting pattern placed inside the image region may be used to increase secure use of the encrypted information stored into an image region. However, very accurate position detecting of the placement position of the encrypted pattern inside the encrypted image region is required to read this type of pattern and decrypt the original information. However, using the markers placed at the four corners of an encrypted image region for detecting the position of the encrypted image region as in the previously described technique does not provide enough accuracy to detect the placement position of an encrypted pattern.